How to read data from serial device which is connected to PC by RS232 ?

#include<errno.h>
#include<windows.h>
#include<termios.h>
#include<unistd.h>
#include<string.h>
#include<stdio.h>
#include<fcntl.h>
#include<stdlib.h>




int set_attributes (int fd, int speed, int parity)
{
        struct termios tty;
        if (tcgetattr (fd, &tty) != 0)
        {
                perror("error\n");
                return -1;
        }

        cfsetospeed (&tty, speed);
        cfsetispeed (&tty, speed);

        tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;

        tty.c_iflag &= ~IGNBRK;
        tty.c_lflag = 0;

        tty.c_oflag = 0;
        tty.c_cc[VMIN]  = 0;
        tty.c_cc[VTIME] = 5;

        tty.c_iflag &= ~(IXON | IXOFF | IXANY);

tty.c_cflag |= (CLOCAL | CREAD);

        tty.c_cflag &= ~(PARENB | PARODD);

 tty.c_cflag |= parity;
        tty.c_cflag &= ~CSTOPB;
        tty.c_cflag &= ~CRTSCTS;

        if (tcsetattr (fd, TCSANOW, &tty) != 0)
        {
                perror("error in setting attributes\n");
                return -1;
        }
        return 0;
}


int set_blocking (int fd, int should_block)
{
        struct termios tty;
        memset (&tty, 0, sizeof tty);
        if (tcgetattr (fd, &tty) != 0)
        {
                perror("error in setting attributes\n");
                return -1;
        }

        tty.c_cc[VMIN]  = should_block ? 1 : 0;
        tty.c_cc[VTIME] = 5;            // 0.5 seconds read timeout

        if (tcsetattr (fd, TCSANOW, &tty) != 0)
                perror("error in setting attributes\n");
}

int main()
{

    char *portname = "/dev/tty";
    int fd = open (portname, O_RDWR | O_NOCTTY | O_SYNC);
    if (fd < 0)
    {
            perror("error\n");
            return -1;
    }

    set_attributes (fd, B9600, 0);
    set_blocking (fd, 0);

    while (1){
             char data[20];
            char buf[100];
            sleep(10);
            int n = read (fd, buf, sizeof buf);
            printf(" the character read from serial port is = %s",buf);
            printf("\n");
        }
        close(fd);
    }